Abductor pollicis longus muscle
The abductor pollicis longus muscle (APL) is one of the extrinsic muscles of the hand. It lies immediately below the supinator muscle and is sometimes united with it.
Origin and insertion
It arises from the lateral part of the dorsal surface of the body of the ulna below the insertion of the Anconæus, from the interosseous membrane, and from the middle third of the dorsal surface of the body of the radius.
Passing obliquely downward and lateralward, it ends in a tendon, which runs through a groove on the lateral side of the lower end of the radius, accompanied by the tendon of the Extensor pollicis brevis, and is inserted into the radial side of the base of the first metacarpal bone.
It occasionally gives off two slips near its insertion: one to the greater multangular bone and the other to blend with the origin of the Abductor pollicis brevis.
Innervation
The abductor pollicis longus muscle is innervated by the posterior interosseous nerve, which is a continuation of the deep branch of the radial nerve after it passes through the supinator muscle. The posterior interosseous nerve is derived from spinal segments C7 & C8.
Action
The chief action of abductor pollicis longus is to abduct the thumb at the carpometacarpal joint, thereby moving the thumb anteriorly.
By its continued action it helps to abduct the wrist.
Variations
More or less doubling of muscle and tendon with insertion of the extra tendon into the first metacarpal, the greater multangular, or into the Abductor pollicis brevis or Opponens pollicis.
See also
Additional images
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Bones of left forearm. Posterior aspect.
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Bones of the left hand. Volar surface.
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Tendons of forefinger and vincula tendina.
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Cross-section through the middle of the forearm.
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Posterior surface of the forearm. Superficial muscles.
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Posterior surface of the forearm. Deep muscles.
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Transverse section across distal ends of radius and ulna.
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Transverse section across the wrist and digits.
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The muscles of the thumb.
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The radial and ulnar arteries.
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External links